PREIMPLANTATION DNA METHYLATION SCREENING (PIMS): POTENTIAL BIOMARKER IN ART

Problem Statement: DNA methylation is known to play an important role during embryogenesis. Previous studies revealed that a large proportion of human preimplantation embryos harbor abnormal DNA methylome. Whether DNA methylation patterns affect the clinical outcome after ART remains unknown.

Materials and Methods: A clinical trial (NCT03642574) of 182 PGTA patients [indications: AMA (≥38yrs), RM with (>2miscarriages), RIF (>3 IVF attempts) and (d) severe OAT] including 800 blastocysts conducted between 2018-2022. PIMS with WGBS protocol was used to measure whole genome DNA methylation and CNV of TE biopsied samples simultaneously. eSET was performed after PIMS. The primary outcome was the LBR while secondary outcomes included clinical pregnancy and first trimester miscarriage rates of patients with embryos of different DNA methylation patterns. Chromosome copy number was calculated with R package (HMMcopy).

Fisher’s exact and two-sided t-test were employed to compare clinical outcomes of different mean TE methylation level (p<0.05).

Results:163 euploid of 800 analyzed embryos were transferred. 57 (31.31%), 13 (7.14%) and 90 (56.25%) patients experienced a pregnancy failure, a pregnancy loss and a live birth respectively.

Significant variation of TE-DNA methylation level was observed irrespective of maternal age (<38: 120 and ≥38 years: 40, p<0.05). Blastocysts with global methylation level of 0.26±0.01 had the highest LBR (31/43 = 72.1%) and clinical pregnancy (33/43 = 76.7%), albeit the lowest miscarriage rate (2/33 = 6.1%). Notably, the embryos with DNA methylation levels between 0.25-0.27 produced significantly higher LBR compared to embryos with methylation levels of 1.13–5.95 (p = 0.02) while the miscarriage rate had an opposite trend 0.04–1.75 (p=0.22). Some embryos had abnormal methylation states in germline ICRs.

Discussion: DNA methylome analysis of preimplantation embryos could be a potential biomarker to prioritize blastocysts for transfer to increase LB and reduce the birth defect rate of imprinting gene disorders after ART although PIMS cannot cover all the ICRs.

Study funding/competing interest(s): The authors claim competing interest of this study.

Abbreviations: [ART-assisted reproductive technology, PIMS-preimplantation DNA methylation screening, PGTA-preimplantation genetic testing for aneuploidy, eSET-elective single embryo transfer, CNV-copy number variant, TE-trophectoderm, WGBS-whole genome bisulfite sequencing, LBR-live birth rate, AMA-advanced maternal age, RM-recurrent miscarriage, RIF-repeated implantation failure, OAT-oligoasthenoteratozoospermia, ICRs-imprinting control regions]